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We can update IPv4 neighbors by using arping command. I have used arping -A -I -c <interface_name> <IP_address_of_interface> with success.

what is the command to update mapping of IPv6 address and mac on router/gateway/nodes. we have observed when IPv6 address is removed from one node N1(RHEL-7.9 Node) and assigned to other node N2(RHEL-7.9 Node), mac address on router(Extreme Networks VDX 8770) dont get updated. It eventually gets updated but that time is not consistent. for this duration N2 is not reachable to gateway.

tushars
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  • Please edit your question to add the operating system of relevant hosts and routers. You tagged this Linux, but your comments indicate something else. – John Mahowald Nov 24 '21 at 14:26

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For service addresses, implement a high availability protocol that can move IP addresses quickly. For example VRRP via keepalived.

To manipulate the neighbor cache on one Linux host, use a command like ip neighbour flush to ${ADDRESS} The kernel will do discovery when it encounters that IP again, do something like ping ${ADDRESS} This does not affect other hosts' neighbor cache. Other platforms and IP stacks have different commands.

IPv6 neighbor advertisement is not using broadcast, it is using a targeted solicited multicast group. One way getting all hosts involved is playing with router advertisements and virtual MAC addresses. In other words, VRRP.

Edit: ND spec allows for unsolicited advertisements to all nodes multicast. But it is an optional MAY, so you might want to trigger it manually. See also on Server Fault: Linux tool for IPv6 unsolicited neighbor advertisements.

John Mahowald
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  • This is not router or failover case or virtual ip, In this case when N1 who has IPv6-ip1 is shut off, and N2 is assigned with IPv6-ip1, mac table on router is still IPv6-ip1-mac-N1. it should be mac-n2. The router is not linux machine. question is from N2 - what can we do to update new mac on router. doing Ping is not working. – tushars Nov 24 '21 at 11:27
  • See edit adding a mention about unsolicited advertisements. How fast do you need cutover to be? ND should figure it out in a leisurely few minutes, but seems like that's not fast enough for you. – John Mahowald Nov 24 '21 at 14:48
  • ndptool with -T is solution. thanks @John for pointer. – tushars Dec 01 '21 at 09:43